Supercomputers and other large computer systems typically include a large number of computer cabinets arranged in close proximity to each other. FIG. 1, for example, illustrates a portion of a prior art supercomputer system 100 having plurality of computer cabinets 110 arranged in a bank. The computer cabinets 110 are arranged in a bank to conserve floor space and increase computational speed by reducing cable lengths between cabinets. Each of the computer cabinets 110 includes a plurality of computer module compartments 118 (identified individually as a first module compartment 118a, a second module compartment 118b, and a third module compartment 118c). Each module compartment 118 holds a plurality of computer modules 112. Like the computer cabinets 110, the computer modules 112 are also positioned in close proximity to each other to conserve space and increase computational speed. Each of the computer modules 112 can include a motherboard electrically connecting a plurality of processors, routers, and other microelectronic devices together for data and/or power transmission.
Many of the electronic devices typically found in supercomputers, such as fast processing devices, generate considerable heat during operation. This heat can damage the device and/or degrade performance if not dissipated during operation. Consequently, supercomputers typically include both active and passive cooling systems to maintain device temperatures at acceptable levels.
To dissipate the heat generated by the computer modules 112, the prior art supercomputer system 100 further includes a plurality of centrifugal fans 120. Each of the centrifugal fans 120 includes a housing 128 mounted to an upper portion of a corresponding computer cabinet 110. Each housing 128 includes a central inlet 122 aligned with an axis of rotation 126, and a circumferential outlet 124 extending around the outside of the housing 128. In operation, the centrifugal fan 120 draws cooling air into the corresponding computer cabinet 110 through a front inlet grill 114 positioned toward a bottom portion of the computer cabinet 110. The cooling air flows upwardly through the computer cabinet 110, past the computer modules 112, and into the central inlet 122. The centrifugal fan 120 then exhausts the cooling air outward in a radial pattern through the circumferential outlet 124.
One problem associated with the prior art supercomputer system 100 is the substantial noise generated by the centrifugal fans 120 during operation. The noise can make working in the vicinity of the computer cabinets 110 difficult or uncomfortable, especially for extended periods of time (e.g., for an 8-hour day). Further, in some instances, the noise can exceed regulations that require, e.g., noise levels of less than 90db in those environments in which persons are working for up to eight hours in a given day.
FIG. 2 is a partially exploded isometric view of a computer cabinet 210 illustrating one method for absorbing fan noise in accordance with the prior art. This method involves use of a recirculation duct 222 having an inlet opening 224 and an outlet opening 226. The recirculation duct 222 is attached to the computer cabinet 210 in such a way that the inlet opening 224 fully encloses the centrifugal fan 120. This arrangement positions the outlet opening 226 directly adjacent to a side inlet grill 214 on the computer cabinet 210. In operation, the recirculation duct 222 routes used cooling air from the centrifugal fan 120 back through the computer cabinet 210 via the side inlet grill 214. Because the recirculation duct 222 is totally closed off from the surrounding environment, much of the noise generated by the centrifugal fan 120 is contained within the recirculation duct 222.
There are a number of shortcomings associated with the prior art noise-reduction solution illustrated in FIG. 2. One shortcoming is the additional floor space consumed by adding the recirculation duct 222 to each of the computer cabinets 210. Not only does this approach consume more floor space, but it also decreases computational speed by increasing cable lengths between adjacent cabinets. Another shortcoming is that the recirculation duct 222 adds substantial back pressure to the flow of cooling air. As a result, the centrifugal fan 120 must operate at a higher speed than in the un-muffled system of FIG. 1 to provide the same air flow rate. Increasing fan speed, however, has the negative effect of increasing noise, power usage, and heat. A further downside associated with the approach illustrated in FIG. 2 is the cost associated with manufacturing, installing, and maintaining the recirculation ducts 222.